OCR Text |
Show resources, information on rodents and methods for their control is required. Economic information.-Economic data of many kinds are missing. Some of the more important data which are badly needed at present include the relative values of different forms of land use, costs of land development practices, returns from various uses of land resources, water costs of vege- tal control of erosion, and costs and returns of operating various types of range livestock enter- prises. Data are needed on per capita water re- quirements. Comparative data are needed on live- stock production on range land versus cultivated or irrigated pastures, and on the economics of using ranges for big game as against livestock produc- tion. Data are also required as to the ultimate economic effect of sedimentation, including the basis for evaluating the loss of nonrenewable space m reservoirs. Conclusion Data now available in the Colorado Basin are sufficient to permit many previously studied projects to proceed. However, full development of the basin and the most efficient use of its water re- sources cannot be attained without a great quan^ tity of additional information over wide fields of interest. It is essential that every agency whose activities are in any way affected by the collection and analysis of data direct its efforts toward the removal of these deficiencies as rapidly as possible, and especially those in which length of record is a material factor. These agencies also should compile and analyze whatever data may be avail- able, and make it available to the people of the basin, their representatives, and those who other- wise serve them. In this, cooperative efforts and cooperative planning of approach are especially im- portant. Organization of this effort should be one of the first tasks of a river basin commission for the Colorado, as suggested by this Commission. 2. Watershed Management The Problem The place of watershed management in pro- grams of water resources development. The Situation About 50 million acres, or 30 percent of the total area of the basin, are in forest or related cover. About 85 percent of this land is in public owner- ship, about half of it in the national forests. About 12.5 million acres are conifer timber at high ele- vations; about 8.5 million acres are aspen; about 9 million, brushlands; and 20 million acres, piiion- juniper. About 40 million acres are grazed. The forest area is the water-yielding area of the basin. It receives heavy precipitation, 18 inches or more, about 75 percent coming in the cooler por- tion of the year. The higher portion including the commercial forest, or about 6 percent of the basin, receives more than 25 inches, of which half is snow. The precipitation which accumulates over a 4- to 6-month period as snow is released in about 6 to 8 weeks, to feed the rivers for the remainder of the year. The balance of the Colorado Basin receives from as little as 2 inches of precipitation annually up to 18 inches, with a general average of about 10 inches. At elevations above 4,000 feet, about half of this comes in the winter as snow. The summer storms often cover only a few square miles and may deliver as much as 2 inches of rain in a few hours. Because these storms frequently have in- -tensities above-theL infiltration capacity of the soil, a considerable part of the precipitation runs off in small local flash floods. These waters occasionally reach a major channel and augment stream flow. Most of the other precipitation is light and is quickly absorbed by plants or lost through evapora- tion. This part of the basin supports various types of semiarid vegetation generally classed as semi- desert shrub, desert shrub, and salt-desert brush- land, and semidesert grass. About 80 percent of the area is in public ownership. For the basin as a whole the forest and other high mountain areas receive about 25 inches of precipita- tion. This area produces as stream flow 7.2 inches annually; the remainder of the basin averages only about 1.3 inches of runoff. One determination of the annual water yield in terms of area shows that 15 percent of the area, producing more than 5 inches of annual runoff, produces 85 percent of the total water supply. About 70 percent of the sediment and 20 percent of the water carried by the Colorado at Lees Ferry originates in the area below the confluence of the Green and Colorado Rivers, or in the driest part of the basin. Federally administered lands consti- tute over 75 percent of the area above Lees Ferry. The present watershed situation must be viewed with knowledge of the history of grazing. Grazing developed early in the West. It began on a large 417 |